LED (Light Emitting Diode, LED) is of a cold light source, having the characters of power saving, lower consumption, fast initiating, mercury free and longer lifetime. After the technical breakthrough for the blue LED at the end of twentieth century, high power LEDs that emit various colors of light are gradually developed and applied in various kinds of products, such as displays, projectors, lighting device, etc. Therefore, LEDs definitely are the light source attracting most attention.
However, since the light emitted from LEDs are monochromatic, this nature limits LEDs, so other light source to replace the light source emitting light with broad band spectrum, such as white light, is still seeking. To solve this problem, it is popular to use one single LED emitting light with shorter wavelength, such as blue light or ultra-violet light, with a phosphor material positioned on the optical path of the LED to transform a part of or all of the light emitted from the LED to the light which spectrum comprises light with longer wavelength, such as green light, red light, etc. Such LED to emit white light is called white LED and it is capable to replace incandescent bulbs or tubes. However, when positioning the conventional lighting device utilizing LEDs, such lighting device is fixed by merely its protruding parts of the lamp cover wedged with the installation spot, and this may cause inconvenient assembling processes or unstable assembly. Therefore, it still needs to find out better solution to these undesired problems.